Well treatment

ABSTRACT

A combustible foamed fluid energized with gaseous fuel and combustion oxidant sources. Also, an energized fluid system, a treatment method using the combustible foamed fluid, and a method to prepare the combustible foamed fluid are disclosed.

RELATED APPLICATION DATA

None.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Foamed fluids, including energized fluids, are often used in downholeapplications such as fracturing and other treatments. In someapplications it may be desired to quickly break, dissipate, and/or flowback foamed fluids in downhole applications, e.g., to implement fractureclosure, or to otherwise rapidly change the properties of the foamedfluid after introducing it into the wellbore.

Foamed fluids may be used in matrix treatments, for example, in theinjection of acidizing agents, chelating agents, paraffins, scaleinhibitors, and so on.

As another example, foamed fluids are often used as carrying fluids toplace proppant and/or other solids into a fracture. The proppant in suchapplications may be homogeneously or heterogeneously placed in afracture, or sometimes in a combination of such placement modalities. InUS 2014/0262264 by Potapenko et al. (also published as WO2014/143490A1), incorporated herein by reference, for example, a methodfor treating a subterranean formation wherein a treatment slurry, whichmay include a foamed carrying fluid among others, is injected into afracture to form a substantially uniformly distributed mixture of solidparticulate and agglomerant; and transforming the substantially uniformmixture into areas that are rich in solid particulate and areas that aresubstantially free of solid particulate, wherein the solid particulateand the agglomerant have substantially dissimilar velocities in thefracture so that the transformation results from the substantiallydissimilar velocities, e.g., during forced fracture closure or flowback.

The industry is thus desirous of improvements to carrying fluids and/orfoamed fluids and/or methods of preparing and using them for variousapplications.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter. The statements made merely provideinformation relating to the present disclosure, and may describe someembodiments illustrating the subject matter of this application.

The present disclosure relates in some embodiments to a combustiblefoamed fluid energized with a gaseous phase comprising both fuel andcombustion oxidant sources, as well as to energized fluid systems, andtreatment methods, relating to the combustible foamed fluid, and methodsto prepare the combustible foamed fluid.

In some embodiments, a treatment method may comprise introducingdownhole a quantity of a treatment fluid comprising a combustible foamedfluid comprising a mixture of a fuel source and a combustion oxidantsource, placing the combustible foamed fluid in a downhole structureunder non-combustion conditions free of an active ignition source, andthereafter igniting the combustible foamed fluid to combust the fuelsource in the downhole structure forming a post-combustion fluid.

In some embodiments, a gas phase of the foam may comprise a mixture ofthe fuel source and the combustion oxidation source. In someembodiments, the mixture may take the form of a gas phase of homogenouscomposition dispersed in a continuous liquid phase, and in furtherembodiments, the gas phase may be heterogeneous, e.g., the fuel sourceand combustion oxidation source may be separately dispersed or dispersedin mixtures of varying proportions.

In some embodiments, the combustion may decompose the foamed fluid. Insome examples, the decomposition may occur such as by vaporizing theliquid phase to an extent that a gas phase or mist is formed, by formingcombustion product(s) that condense to liquid(s), or are miscible withthe liquid phase, by thermally decomposing a foaming agent, by forming adefoaming agent, or the like, or a combination thereof.

In some embodiments, the method may further comprise cooling thepost-combustion fluid to a reduced specific volume relative to thecombustible foamed fluid. In some examples, the post combustion fluidmay contain a lower proportion of non-condensable, non-soluble gases atthe ambient formation pressure and temperature conditions, e.g., amixture of hydrogen and oxygen will form water, which upon equilibrationto ambient formation pressure and temperature conditions and at leastpartial condensation, will reduce the total volume of the resultantfluid relative to that of the pre-combustion foam.

In some embodiments of the method, the treatment fluid may furthercomprise proppant and/or the downhole structure may comprise a fracture,e.g., above a fracturing pressure of the formation. In some examples thetreatment fluid may be a fracturing fluid, e.g., a pad stage, proppantstage, flush stage, or the like.

In some embodiments, the treatment fluid may further comprise a matrixtreatment agent, and/or the downhole structure may comprise a formationmatrix, e.g., below a fracturing pressure of the formation.

In some embodiments, the combustion may improve the effectiveness oftreatment, reduce flowback volumes, minimize formation damage,accelerate return to production following treatment, or the like.

In some embodiments, the fuel source is selected from hydrogen,hydrocarbon gases, or a mixture thereof, and/or the combustion oxidantsource may comprise oxygen, e.g., molecular oxygen, in the form of air,oxygen-enriched air, purified oxygen, oxygen formed by chemicalreaction, or the like.

In some embodiments, the combustible foam is prepared at a surfacelocation and introduced into a wellbore, and in other embodiments, thecombustion oxidant source is introduced into the wellbore in a firststream separate from a second stream comprising the fuel source, and thefirst and second streams are mixed downhole to form the combustiblefoamed fluid.

The present disclosure also relates to embodiments of an energized fluidsystem comprising a combustible foamed fluid comprising a combustiblegaseous mixture dispersed in a continuous liquid phase, a downholestructure to receive the combustible foamed fluid under non-combustionconditions free of an active ignition source, and an ignition source incommunication with the downhole structure activatable to initiatecombustion of the dispersed gaseous mixture. In some embodiments, thecombustible foamed fluid is substantially free of inert gas, e.g.,comprised of less than 5 vol % inert gases such as nitrogen, e.g., themixture may be comprised of oxygen mixed with a fuel source selectedfrom hydrogen, hydrocarbon gases, and the like, including combinationsthereof.

In some embodiments, the structure may comprise a wellbore, a fracture,a formation matrix, or the like.

In some embodiments, the ignition source may comprise an igniter, e.g.,an electrical or chemical igniter, and/or the energized fluid system mayfurther comprise a controller to activate the ignition source, whichcontroller may automatically activate the ignition source, e.g., after apredetermined time period or at predetermined pressure, temperature, orchemical or other downhole conditions, and/or which may be remotelylocated, e.g., downhole or at the surface, for remotely activating theignition source.

The present disclosure also relates to embodiments of a method,comprising dispersing a gaseous fuel source and a gaseous combustionoxidant source into a continuous liquid phase to form a combustiblefoamed fluid, and isolating the combustible foamed fluid in a downholestructure under non-combustion conditions free of an active ignitionsource. In some embodiments, the gaseous fuel source and gaseouscombustion oxidant may be delivered in separate streams through awellbore and mixed downhole, or the fuel source and combustion oxidantmay be mixed at the surface and the mixture pumped downhole, e.g., in acombustible foam prepared at the surface.

In some other embodiments, the method may comprise passing the liquidphase through an electrolysis cell, either downhole or at the surface,to electrolytically generate the fuel and combustion oxidant sources,e.g., where the liquid phase is aqueous, the gaseous fuel source may behydrogen, and the gaseous combustion oxidant may be oxygen.

In some embodiments, the downhole structure comprises a fracture above afracturing pressure, or a formation matrix below the fracturingpressure, or a combination of a fracture and a formation matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

None.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present disclosure. However, it may beunderstood by those skilled in the art that the methods of the presentdisclosure may be practiced without these details and that numerousvariations or modifications from the described embodiments may bepossible. Certain statements made in this section may merely providebackground information related to the present disclosure, but may notconstitute prior art.

At the outset, it should be noted that in the development of any suchactual embodiment, numerous implementation-specific decisions may bemade to achieve the developer's specific goals, such as compliance withsystem related and business related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time consuming but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure. In addition, the compositionused/disclosed herein can also comprise some components other than thosecited. In the summary and this detailed description, each numericalvalue should be read once as modified by the term “about” (unlessalready expressly so modified), and then read again as not so modifiedunless otherwise indicated in context. Also, in the summary and thisdetailed description, it should be understood that a range listed ordescribed as being useful, suitable, or the like, is intended to includesupport for any conceivable sub-range within the range at least becauseevery point within the range, including the end points, is to beconsidered as having been stated. For example, “a range of from 1 to 10”is to be read as indicating each possible number along the continuumbetween about 1 and about 10. Furthermore, one or more of the datapoints in the present examples may be combined together, or may becombined with one of the data points in the specification to create arange, and thus include each possible value or number within this range.Thus, (1) even if numerous specific data points within the range areexplicitly identified, (2) even if reference is made to a few specificdata points within the range, or (3) even when no data points within therange are explicitly identified, it is to be understood (i) that theinventors appreciate and understand that any conceivable data pointwithin the range is to be considered to have been specified, and (ii)that the inventors possessed knowledge of the entire range, eachconceivable sub-range within the range, and each conceivable pointwithin the range. Furthermore, the subject matter of this applicationillustratively disclosed herein suitably may be practiced in the absenceof any element(s) that are not specifically disclosed herein.

The following definitions are provided in order to aid those skilled inthe art in understanding the detailed description. Terms may also bedefined elsewhere in the specification and/or claims.

The term “downhole structure” includes any subterranean arrangement ofmaterials below the surface that may hold, contain, be filled with, orallow the passage of a fluid, such as, without limitation, wellbore,drill pipe or string, tubing, casing, wireline, screen, annulus,fracture, tool, matrix, cavern, lost circulation zone, vug, pores,perforations, and the like. A downhole structure thus refers to anydownhole feature without limitation through which fluid may flow orpass, including, but not limited to, a formation matrix, screen or otherporous media, or surface thereof, fracture, formation void, vug,wormhole, fluid loss zone, chamber, perforation, valve, opening, or aline, tubing pipe or similar flow conduit, such as casing, tubing(including coiled tubing), drill pipe, and including any annulus orspace between any of such structures, and any combinations thereof, orthe like.

The term “wellbore” is a drilled hole or borehole, including theopenhole or uncased portion of the well that is drilled during atreatment of a subterranean formation. The term “wellbore” does notinclude the wellhead, or any other similar apparatus positioned over thewellbore or at the surface. The wellbore or other downhole structure maybe horizontally or vertically disposed, or sloped.

The term “treatment” or “treating” refers to any subterranean operationthat uses a fluid in conjunction with a desired function and/or for adesired purpose. The term “treatment” or “treating” does not imply anyparticular action by the fluid.

The term “injecting” describes the introduction of a new or differentelement into a first element. In the context of this application,injection of a fluid, solid or other compound may occur by any form ofphysical introduction, including but not limited to pumping.

The term “fracturing” refers to the process and methods of breaking downa geological formation and creating a fracture, i.e., the geologicalformation around a well bore, in order to increase production rates froma hydrocarbon reservoir. Fracture “creation” includes initiation of anew fracture or fracture branch, as well as propagation and/or expansionof a fracture. The fracturing methods otherwise use techniques known inthe art.

“Partial fracturing” refers to the formation of one or especially aplurality fractures formed within a formation which do not communicatedirectly to the wellbore, or do not connect to a fracture thatcommunicates directly to the wellbore and/or form a part of a fracturenetwork isolated from direct communication to the wellbore.

The term “matrix acidizing” refers to a process where treatments of acidor other reactive chemicals are pumped into the formation at a pressurebelow which a fracture can be created. The matrix acidizing methodsotherwise use techniques known in the art.

The terms “combustible fluid,” “auto-combustible fluid,” and similarterms are used interchangeably herein refer to a mixture comprising acombustion-sustaining mix of fuel and oxidant sources, i.e., throughwhich a flame can be propagated in situ by an ignition source withoutthe requirement of exogenous reactants, as in an enclosed container.

The term “combustion” refers to the act or instance of burning of a fuelwith an oxidant to release energy, usually in the form of heat andlight, and also including the terms “detonation” and “explosion”referring to combustion in which the flame propagation exceeds theacoustic velocity of the reactant media, as well as “ignition” referringto the initiation of combustion.

The term “non-combustion conditions” refers to a stable combustiblefluid that is not in fluid communication with a flame or other activeignition source such as a static electrical spark.

The term “ignition source” refers to a composition, device or mechanismcapable of initiating combustion of a combustible fluid.

The terms “energized fluid” and “foam” refer to a fluid which whensubjected to a low pressure environment liberates or releases gas fromsolution or dispersion, for example, a liquid containing dissolvedgases. Foams or energized fluids are stable mixtures of gases andliquids that form a two-phase system. Foam and energized fluids aregenerally described by their foam quality, i.e. the ratio of gas volumeto the foam volume (fluid phase of the treatment fluid), i.e., the ratioof the gas volume to the sum of the gas plus liquid volumes. If the foamquality is between 52% and 95%, the energized fluid is usually calledfoam. Above 95%, foam is generally changed to mist. In the presentpatent application, the terms “energized fluid” and “foam” may be usedinterchangeably herein, and refer to any stable mixture of gas andliquid, regardless of the foam quality unless context indicatesotherwise. Energized fluids comprise any of: (a) Liquids that atdownhole conditions of pressure and temperature are close to saturationwith a species of gas; for example the liquid can be aqueous and the gasnitrogen or carbon dioxide or hydrogen or oxygen or air or methane orfuel gas, etc.; associated with the liquid and gas species andtemperature is a pressure called the bubble point, at which the liquidis fully saturated; at pressures below the bubble point, gas emergesfrom solution; (b) Foams, consisting generally of a gas phase, anaqueous phase and an optional solid phase; at high pressures the foamquality is typically low (i.e., the non-saturated gas volume is low),but quality (and volume) rises as the pressure falls; additionally, theaqueous phase may have originated as a solid material and once the gasphase is dissolved into the solid phase, the viscosity of solid materialis decreased such that the solid material becomes a liquid; or (c)Liquefied gases.

“Viscosity” as used herein unless otherwise indicated refers to theapparent dynamic viscosity of a fluid at a temperature of 25° C. andshear rate of 170 s⁻¹. As used herein, when not used in context relativeto a higher viscosity fluid, a “low viscosity” fluid or phase, e.g., alow viscosity carrier or liquid phase, refers to one having a viscosityless than 50 mPa-s at a shear rate of 170 s⁻¹ and a temperature of 25°C.

As used herein, “slurry” refers to an optionally flowable mixture ofparticles dispersed in a fluid carrier. The terms “flowable” or“pumpable” or “mixable” are used interchangeably herein and refer to afluid or slurry that has either a yield stress or low-shear (5.11 s⁻¹)viscosity less than 1000 Pa and a dynamic apparent viscosity of lessthan 10 Pa-s (10,000 cP) at a shear rate 170 s⁻¹, where yield stress,low-shear viscosity and dynamic apparent viscosity are measured at atemperature of 25° C. unless another temperature is specified explicitlyor in context of use.

The term “particulate” or “particle” refers to a solid 3-dimensionalobject with maximal dimension less than 1 meter, or less than 0.1 meteror less than 0.01 meter. Here, “dimension” of the object refers to thedistance between two arbitrary parallel planes, each plane touching thesurface of the object at least at one point.

In embodiments, the combustible foamed fluid may comprise multimodalparticles. As used herein “multimodal” refers to a plurality of particlesizes or modes which each has a distinct size or particle sizedistribution, e.g., proppant and fines. As used herein, the termsdistinct particle sizes, distinct particle size distribution, ormulti-modes or multimodal, mean that each of the plurality of particleshas a unique volume-averaged particle size distribution (PSD) mode. Thatis, statistically, the particle size distributions of differentparticles appear as distinct peaks (or “modes”) in a continuousprobability distribution function. For example, a mixture of twoparticles having normal distribution of particle sizes with similarvariability is considered a bimodal particle mixture if their respectivemeans differ by more than the sum of their respective standarddeviations, and/or if their respective means differ by a statisticallysignificant amount. In an embodiment, the particles contain a bimodalmixture of two particles; in an embodiment, the particles contain atrimodal mixture of three particles; in an embodiment, the particlescontain a tetramodal mixture of four particles; in an embodiment, theparticles contain a pentamodal mixture of five particles, and so on.Representative references disclosing multimodal particle mixturesinclude U.S. Pat. No. 5,518,996, U.S. Pat. No. 7,784,541, U.S. Pat. No.7,789,146, U.S. Pat. No. 8,008,234, U.S. Pat. No. 8,119,574, U.S. Pat.No. 8,210,249, US 2010/0300688, US 2012/0000641, US 2012/0138296, US2012/0132421, US 2012/0111563, WO 2012/054456, US 2012/0305245, US2012/0305254, US 2012/0132421, PCT/RU2011/000971 and U.S. Ser. No.13/415,025, each of which are hereby incorporated herein by reference.

“Proppant” refers to particulates that are used in well work-overs andtreatments, such as hydraulic fracturing operations, to hold fracturesopen following the treatment. In some embodiments, the proppant may beof a particle size mode or modes in the slurry having a weight averagemean particle size greater than or equal to about 100 microns, e.g., 140mesh particles correspond to a size of 105 microns. In furtherembodiments, the proppant may comprise particles or aggregates made fromparticles with size from 0.001 to 1 mm. All individual values from 0.001to 1 mm are disclosed and included herein. For example, the solidparticulate size may be from a lower limit of 0.001, 0.01, 0.1 or 0.9 mmto an upper limit of 0.009, 0.07, 0.5 or 1 mm. Here particle size isdefined is the largest dimension of the grain of said particle.

“Gravel” refers to particles used in gravel packing, and the term issynonymous with proppant as used herein. “Sub-proppant” or “subproppant”refers to particles or particle size or mode (including colloidal andsubmicron particles) having a smaller size than the proppant mode(s);references to “proppant” exclude subproppant particles and vice versa.In an embodiment, the sub-proppant mode or modes each have a weightaverage mean particle size less than or equal to about one-half of theweight average mean particle size of a smallest one of the proppantmodes, e.g., a suspensive/stabilizing mode.

As used herein, proppant loading is specified in weight of proppantadded per volume of treatment stream to which it is added, e.g., kg/L(ppa=pounds of proppant added per gallon of carrier fluid). Othermaterials in the treatment fluid are generally expressed in terms of g/Lbased on the total volume of the treatment fluid in which they arepresent (ppt=pounds of material per thousand gallons of treatmentfluid).

The term “fiber” refers to elongated particles having an aspect ratio(ratio of length longest dimension to diameter or shortest dimension) ofat least 10. The term “carrier fibers” refers to fibers which aresuitable at an appropriate loading for assisting in the transport ofproppant into a fracture, e.g., either during initiation, propagation orbranching of the fracture. The term “non-bridging fibers” refers tofibers which are suitable for use in a carrier fluid at specifiedconditions and loadings generally without forming a bridge in the flowpath of interest. “Bridging fibers” refers to fibers that do not havethe non-bridging quality and/or non-bridging fibers used atbridge-inducing loading rates. Carrier fibers may be bridging ornon-bridging.

In the present disclosure, the terms “low temperature fibers”, “midtemperature fibers” and “high temperature fibers” may be used toindicate the temperatures at which the fibers may be used for delayeddegradation, e.g., by hydrolysis, at downhole conditions. Lowtemperatures are typically within the range of from about 21° C. (70°F.) to about 79° C. (175° F.); mid temperatures typically from about 80°C. (176° F.) to about 149° C. (300° F.); and high temperatures typicallyabout 150° C. (302° F.) and above, or from about 150° C. (302° F.) toabout 232° C. (450° F.).

As used herein, an agglomerant is any material, such as fibers, flocs,flakes, discs, rods, stars, etc., for example, which may beheterogeneously distributed in the fracture and have a differentmovement rate, and/or cause some of the first solid particulate to havea different movement rate, which may be faster or preferably slower withrespect to the settling of the first solid particulate and/or clusters.As used herein, an agglomerant may also be or include an “anchorant,”referring to a material, a precursor material, or a mechanism, thatinhibits movement such as settling, or preferably stops movement, ofparticulates or clusters of particulates in a fracture, whereas an“anchor” refers to an anchorant that is active or activated to inhibitor stop the movement. As used herein, the term “flocs” includes bothflocculated colloids and colloids capable of forming flocs in thetreatment slurry stage.

Some embodiments of this disclosure relate to systems and methods totreat a well and/or downhole structure with a foamed fluid comprising acombustible gaseous phase, e.g., for hydraulic fracturing, matrixtreatments, wellbore cleanout operations, and the like. Combustion ofthe fluid as a process feature in some embodiments generally results inan energy release from the exothermic combustion process and a transienttemperature, pressure and/or volume increase of the fluid, generallyfollowed by a return to ambient downhole temperature and pressureconditions.

In some specific embodiments, especially where the combustion productsmay include condensable components such as water and/or apost-combustion gaseous phase of lower volume, an ultimate reduction ofthe overall fluid volume relative to the combustible foamed fluid justprior to combustion. For example, oxygen, hydrogen and lighthydrocarbons such as methane, ethane or the like may occur in thegaseous phase of the combustible foamed fluid, but upon combustion,there may be fewer gaseous products on a molar or volumetric basis, andalso, some common combustion products such as water may condense largelyto liquid phase at the ambient downhole pressure and temperature, whilecarbon dioxide may dissolve in and/or be miscible with other downholeliquids. For example, a gaseous mixture of stoichiometric oxygen andhydrogen (1:2 molar ratio) may form almost entirely into watercondensate, which has a negligible volume relative to the gaseousreactants. Further, transient pressure or temperature increases duringthe combustion may lead to the escape of some gaseous phase, e.g.,through the wellbore, or into adjacent porous formation matrix or otherporous material, or into fractures created by the combustion, or thelike, and the escaped fluid may not, or not fully return post-combustionto the situs of the original combustible foamed fluid.

In some embodiments, the combustion of the combustible fluid in adownhole structure such as a wellbore, annulus, formation fracture,formation matrix, or the like, may enhance the effectiveness of one ormore treatment attributes, such as, for example, more desirable proppantplacement (e.g., well-defined pillars and channels), reduced formationdamage, reduced flowback volume, shortening of the unproductive periodof time for the treatment and/or more rapid initiation or return of theproduction of reservoir fluids following treatment, and the like.

In various embodiments, the properties of the combustible foamed fluid,including the combustion parameters such as dynamics and kinetics, arein various embodiments controlled by foam quality, size and sizedistribution of the dispersed fluid phase droplets, fluid chemistry,composition of the gaseous and/or liquid phases, and the like.

In specific embodiments of the present disclosure, the combustiblefoamed fluid is used for performing matrix treatments, e.g., belowfracturing pressure of the subterranean formation and/or in conjunctionwith fracturing. Examples of such treatments include matrix acidizing,injection of chelating agents into the matrix, injection of paraffininto the matrix, injection of scale inhibitors into the matrix, etc. Inmatrix treatment embodiments, at or near the conclusion of the treatmentprocess, all of a significant portion of the combustible foamed fluidmay remain in various openings inside the treated formation, with thesize and configuration of the openings defined by the type of thetreatment as well as the formation geology: acid etched fractures,hydraulic fractures, wormholes, open natural fractures, caverns, vugs,interstices, etc. When the combustible foamed fluid is ignited andcombustion otherwise occurs in accordance with embodiments of thepresent disclosure, the combustion of the fluid in such openings mayresult in increasing effectiveness of the performed treatment, such as,for example, by reducing the flowback volume, and/or by at leastpartially fracturing the formation, e.g., due to an initial pressureincrease during the combustion process that can locally exceed thefracture pressure as well as an initial temperature increase that canlocally reduce the fracture pressure of the formation, or the like.

The following discussion is directed in the main to hydraulic fracturingembodiments, by way of illustration and example, and is not intended tothereby limit the scope of the disclosure or claims, it being understoodthat the systems and methods described herein as well as the principlesthereof may be equally applicable, with or without appropriatemodification, to other downhole treatments and structures such as matrixtreatments, wellbore treatments, etc. In hydraulic fracturing, thecombustible foamed fluid may be employed in the initiation, propagationor other creation of a fracture, such as, for example, in one, or acombination, or all, of a pad or pre-pad stage, a proppant stage, anon-proppant stage, spacer stage, tail-in stage, flush stage, or thelike.

The combustible foamed fluid in various embodiments may comprise aliquid phase or phases, a gaseous phase or phases, fuel source(s),combustion oxidant source(s), inert(s) such as nitrogen, argon, and thelike, combustion modifier(s), including inhibitors, retardants,accelerants, and/or initiators, foaming agent(s), gelling agent(s),proppant(s), fluid loss additive(s), sub-proppant(s), fiber(s),polymer(s), crosslinker(s), surfactant(s), breaker(s), biocide(s),friction reducer(s), corrosion inhibitor(s), temperature stabilizer(s),clay stabilizer(s), chelant(s), scale inhibitor(s), diverting agent(s),proppant or other solid flowback control additive(s), agglomerant(s),and the like, including multifunctional components that perform two ormore of these functions. For example, nitrogen gas is an inert gas whichcan inhibit flame propagation as well as reduce any transienttemperature increase following combustion due to a lower heating valueof the gaseous phase of the fluid. Lower foam quality, i.e., a highervolumetric proportion of water or other non-flammable liquid, canlikewise be used in some embodiments to inhibit flame propagation andreduce the transient temperature and/or pressure increases due to alower heating value and the latent heat for volatilization of the liquidcomponent of the foam.

The liquid phase of the combustible foamed fluid may be aqueous in someembodiments, or can be non-aqueous, or a mixture, such as an oil/wateremulsion or invert emulsion. The presence of fuel materials such ashydrocarbons and/or oxidant materials such as peroxides can alsoaccelerate the combustion process and/or increase the resultingtransient pressures and temperatures, whereas the presence ofnon-flammable components such as brine can serve to inhibit thecombustion process. In some embodiments, the carrier fluid comprisesbrine, e.g., sodium chloride, potassium bromide, ammonium chloride,potassium choride, tetramethyl ammonium chloride and the like, includingcombinations thereof. In some embodiments the diluted stream maycomprise oil, including synthetic oils, e.g., in an oil based or invertemulsion fluid.

The combustible foamed fluid may be mixed at the surface before orduring pumping downhole, or one or more components may be delivereddownhole separately, e.g., in separate flow paths or containers, andmixed downhole, e.g., in the wellbore or in or adjacent the formation,or one or more components may be generated or formed downhole, e.g., byelectrolysis, chemical reaction, or the like. For example, the gaseousfuel source may be separated from the combustion oxidant source by usingseparate lines, tubing, coiled tubing, including concentricalcoil-tubing (e.i. containing one or more tubing inside the coil tubingitself), or the like, and a downhole mixer to combine or mix theseparate streams together prior to introduction into the formation. Insome embodiments, mixing or other formation of the combustible mixtureis caused to occur below (relative to the surface) a flow directioncheck valve, flame arrester or the like to inhibit combustion throughthe wellbore to the surface, or combustion of the combustible foamedfluid or components at or adjacent the surface can be inhibited bylocating a flame arresting device in the wellbore, e.g., above theignition source. In some embodiments, the wellhead and/or surfaceequipment are designed to withstand any pressure and/or temperatureincreases that might result from combustion of the combustible foamedfluid, whether the combustion is planned or occurs inadvertently, e.g.,after shut in of the well and/or during pumping, e.g., after shut in ofthe well and/or during pumping of the combustible foamed fluid.

Electrolysis of water or another aqueous liquid in some embodiments canbe used to generate a mixture of hydrogen and oxygen gases according tothe reaction: 2H₂O→2H₂+O₂. Electrolysis can be performed at the surfaceor downhole in an electrolytic cell by passing an electrical currentbetween electrodes in contact with the aqueous liquid. In someembodiments, either direct current (DC) or alternating current (AC) canbe used, including a variable voltage such as a frequency modulatedvoltage, e.g., in the frequency range of from 1 Hz to 1 MHz. The mixtureof hydrogen and oxygen in the gaseous phase of the foamed fluid can bestoichiometric or approximately stoichiometric (due to differentsolubilities or reactivities etc.) in the foamed fluid media, and insome embodiments may be the only gases introduced into the foamed fluid,or can be used with other gaseous materials.

In some embodiments, the combustible foamed fluid is placed in thefracture or other downhole structure under non-combustion conditionsfree of an active ignition source, and thereafter ignited. In contrastto methods employing a downhole burner or other combustion device inwhich a steady state or moving flame front is maintained as in drycombustion, reverse combustion, wet combustion and like in situcombustion techniques, in some embodiments, the combustible foamed fluidherein is not ignited and/or combustion initiated until after the fluidis placed in the fracture or otherwise used to at least partiallycomplete a treatment function, e.g., fracture creation, matrixacidization, or the like. At some point during performance of thefracture treatment, i.e., during placement into the downhole structure,or after completion of the fracturing treatment, i.e., after placementinto the downhole structure, a combustion process is initiated in thegaseous phase of the combustible foamed fluid.

In some embodiments, ignition of the combustible foamed fluid isachieved by one or more of surface ignition and propagation through thewellbore or tubing installed in the wellbore; downhole ignition with anelectrical arc or other igniter which may be deployed via coiled tubing,wireline or the like; chemical systems such as Mg/H₂O, Al/NaOH,KMnO₄/glycerol, or the like, that increase the temperature at a point orregion of the combustible foamed fluid above the ignition point, e.g.,by encapsulating one or more reactants wherein a coating dissolves,melts or is crushed at downhole conditions such as pressure,temperature, pH, fracture closure, or the like; the use of explosivematerials that can detonate downhole.

In some embodiments, the direction of the combustion or flame front(s)during the combustion process may be selected by the placement of theignition source, e.g., at the tip of the fracture for a “reverse”combustion propagation toward the wellbore, at a location near thewellbore-fracture junction for “forward” propagation through thefracture away from the wellbore toward the tip(s), and/or placement of aplurality of ignition sources at multiple locations to form a pluralityof propagation zones corresponding to each of the respective ignitionsources, which may or may not have propagation fronts that meetintermediate the ignition sources. According to some embodiments,proppant may accumulate to form pillars or ridges at the outer edges ofthe respective propagation zones and/or where the propagation frontsmeet between adjacent ones of the ignition sources.

In some embodiments, combustion of the combustible foamed fluid in afracture may result in a reduction of the volume of the foamed fluidplaced in the formation fracture, e.g., a fracture network, and achieverelatively instantaneous fracture closure, e.g., especially relative toa shut-in procedure where the fracturing fluid may need a period oftime, first to chemically break and/or then to generally only graduallypermeate into the formation matrix.

Rapid fracture closure in some fracturing embodiments can assist inachieving and/or retaining a desired proppant placement modality, forexample, by reducing the opportunity for proppant to settle orexcessively settle in the formation. In some embodiments, the proppantis “frozen” in place by rapid fracture closure, e.g., trapping theproppant in a relatively homogeneous distribution that preserves a highporosity and/or conductivity for fluid to flow through the intersticesin the proppant pack, or trapping the proppant in pillars spaced apartby conductive flow channels between the proppant pillars or islands.

In some embodiments, the fracturing method or system optionally includesisolating the fracture from fluid communication from the fracture priorto or during combustion of the foamed fluid in the fracture, e.g., usingisolation sleeves, isolation valves, or diversion plugs. Isolation ofthe fracture can inhibit fluid flowback during the combustion process,and inhibit turbulence and/or fluid flow during combustion that mightotherwise result in movement of the proppant within the fracture fromits desired location.

In some embodiments, fluid communication between the wellbore andanother downhole structure in which the combustible fluid has beenplaced, such as a fracture, is established during the combustion of thecombustible foamed fluid. A transient pressure increase resulting fromthe combustion in some embodiments may create or increase fluid flowinto the wellbore from the other downhole structure to facilitate fluidflowback, facilitate cleanup (e.g., by entrainment and expulsion of flowdamaging materials), and/or or facilitate proppant placement, e.g. byforming or assisting in the formation of proppant pillars, or by placingand/or consolidating proppant in a gravel pack in a screen annulusand/or in a near wellbore portion of the fracture.

In some embodiments, a proppant injection stage comprises alternatingproppant-rich and proppant-lean or proppant-free substages, or otherwisealternating the characteristics between substages, so as to form apillar-channel proppant placement configuration. The present disclosurein some embodiments includes injecting the combustible foamed fluid,e.g., in or with the proppant injection stage, wherein the combustionoperation facilitates quickly closing the fracture and preserves thepillar-channel proppant placement. According to some embodiments, theproppant stage(s) may be injected into a fracture system using any oneof the available proppant placement techniques, including heterogeneousproppant placement techniques, wherein the low viscosity treatment fluidherein is used in place of or in addition to any proppant-containingtreatment fluid, such as, for example, those disclosed in U.S. Pat. No.3,850,247; U.S. Pat. No. 5,330,005; U.S. Pat. No. 7,044,220; U.S. Pat.No. 7,275,596; U.S. Pat. No. 7,281,581; U.S. Pat. No. 7,325,608; U.S.Pat. No. 7,380,601; U.S. Pat. No. 7,581,590; U.S. Pat. No. 7,833,950;U.S. Pat. No. 8,061,424; U.S. Pat. No. 8,066,068; U.S. Pat. No.8,167,043; U.S. Pat. No. 8,230,925; U.S. Pat. No. 8,372,787; US2008/0236832; US 2010/0263870; US 2010/0288495; US 2011/0240293; US2012/0067581; US 2013/0134088; EP 1556458; WO 2007/086771; SPE 68854:Field Test of a Novel Low Viscosity Fracturing Fluid in the Lost HillsFields, California; and SPE 91434: A Mechanical Methodology of ImprovedProppant Transport in Low-Viscosity Fluids: Application of aFiber-Assisted Transport Technique in East Texas; each of which ishereby incorporated herein by reference in its entirety.

According to some embodiments herein, the proppant injection stagecomprises alternating the injection of a combustible foamed fluidsubstage with another substage comprised of a non-combustible fluid,which may be a liquid or a foam, e.g., a foam of similar quality,density, and/or viscosity to inhibit mixing between the alternatingadjacent substages. The proppant or other materials or components may beotherwise homogeneous or of similar content between the alternatingsubstages, or they may have different concentrations of proppant,agglomerant, anchors or the like. Upon placement and/or combustion ofthe alternating substages in the fracture, optionally wherein thesubstages are segregated within the fracture, according to someembodiments, the proppant may accumulate to form pillars selectivelywithin the combustible foam substages, or within the non-combustiblefoam substages, or within both, or at interfaces between the combustibleand non-combustible foam substages. In some embodiments, the combustiblefoamed fluid substages may each comprise at least one respectiveignition source. In some embodiments, the combustible foamed fluidsubstages are ignited simultaneously, sequentially or in a combinationthereof.

In some embodiments, as in, for example, US 2014/0262264 by Potapenko etal. (also published as WO 2014/143490A1), incorporated herein byreference, a method for treating a subterranean formation comprisesinjecting a treatment slurry, which includes a combustible foamedcarrying fluid according to embodiments of the present disclosure, intoa fracture to form a substantially uniformly distributed mixture ofsolid particulate and agglomerant; initiating combustion of thecombustible foamed fluid in the fracture; and transforming thesubstantially uniform mixture into areas that are rich in solidparticulate and areas that are substantially free of solid particulate,wherein the solid particulate and the agglomerant have substantiallydissimilar velocities in the fracture so that the transformation resultsfrom the substantially dissimilar velocities. In some embodiments, thecombustion induces a flow of fluid in the fracture to initiate transportand/or promote further transport the solid particulate and theagglomerant at the substantially dissimilar velocities. In someembodiments, the combustion induces rapid fracture closure tosubstantially preserve, i.e., inhibit degrading or blurring of, thesolid particulate-rich and solid particulate-lean areas. In someembodiments, the combustion induces a flow of fluid in the fracture totransport or further transport the solid particulate and the agglomerantat the substantially dissimilar velocities. In some embodiments, thecombustion initially induces a flow of fluid in the fracture to initiatetransport and/or promote further transport the solid particulate and theagglomerant at the substantially dissimilar velocities, and subsequentlythen induces rapid fracture closure to substantially preserve (orinhibit degrading or blurring of) the solid particulate-rich and solidparticulate-lean areas.

According to some embodiments herein, the combustion of the combustiblefoamed fluid may create fractures in the subterranean formation, e.g.,initiate new fractures and/or extend existing fractures. In someembodiments, combustion of the combustible foamed fluid in the downholestructure may at least temporarily raise the pressure of the fluid, andin some embodiments the elevated pressure may exceed a fracture pressureof the adjacent formation. In some embodiments, extension of fracturesmay be coordinated with isolation of the fracture from the wellboreduring combustion of the combustible foamed fluid in the existing orcreated fracture. In some embodiments, initiation of new fractures maybe coordinated with isolation of any pre-existing fractures from awellbore during combustion of the combustible foamed fluid in thewellbore, and/or by isolating the combustible foamed fluid to aninterval of the wellbore and igniting the combustible foamed fluid tocreate an at least temporary increase in pressure above the fracturingpressure of the formation.

In further embodiments according to the present disclosure, thecombustion may at least temporarily increase the temperature of thepost-combustion fluid. In some embodiments, the treatment fluid maycomprise a thermally sensitive viscosity or rheology modifier, and thetemperature increase can effectively break the treatment fluid, i.e.,reduce the viscosity and/or gel strength of the fluid or a portionthereof. In some embodiments, the combustible foamed fluid may comprisea thermally sensitive foaming system, e.g., foaming agents orstabilizers or liquid surface tension that cease to support the foamstructure at the elevated temperature, and the temperature increase,alone or together with the changes in foam quality associated withcombustion (at least transient changes and/or fluctuations in thegas:liquid ratio due to temporary expansion and ultimate reduction ofthe gas volume) can effectively destabilize and/or degrade the foam.

In some embodiments, the present disclosure can use a treatment fluidthat is thermally stable at the expected downhole conditions of use, butreadily broken, degraded, or destabilized, at the fluid temperatureprofile resulting from combustion of the combustible foamed fluid usedas the treatment fluid or as a sufficient portion of the treatment fluideffective to provide the fluid temperature. For example, treatmentfluids such as fracturing fluids are designed by taking intoconsideration the downhole temperature and the viscosifiers needed tomeet the viscosity requirements during a fracturing treatment at thattemperature, and also by considering the requirements for breaking aswell as fluid destruction requirements in the end of it. Taking intoaccount that combustion temperature may be relatively higher than thatof the ambient formation, in some embodiments a fracturing fluid may beused having a composition normally considered as too damaging orotherwise unsuitable for use due to a low ambient formation temperature.In a specific embodiment of the present disclosure a single compositionof such fracturing fluid can be used for treating wells regardless oftheir temperature range, e.g., a “universal” fracturing fluid can beused over a wide range of formation temperatures.

In some embodiments herein, a combustible foamed fluid may compriseproppant, or be used or pumped with another stage or substage comprisingproppant in a fracturing operation. The proppant, when present, can benaturally occurring materials, such as sand grains. The proppant, whenpresent, can also be man-made or specially engineered, such as coated(including resin-coated) sand, modulus of various nuts, high-strengthceramic materials like sintered bauxite, etc. In some embodiments, theproppant of the current application, when present, has a density greaterthan 2.45 g/mL, e.g., 2.5-2.8 g/mL, such as sand, ceramic, sinteredbauxite or resin coated proppant. In some embodiments, the proppant ofthe current application, when present, has a density greater than orequal to 2.8 g/mL, and/or the treatment fluid may comprise an apparentspecific gravity less than 1.5, less than 1.4, less than 1.3, less than1.2, less than 1.1, or less than 1.05, less than 1, or less than 0.95,for example. In some embodiments a relatively large density differencebetween the proppant and carrier fluid may enhance proppant settlingduring the clustering phase, for example.

In some embodiments, the proppant of the current application, whenpresent, has a density less than or equal to 2.45 g/mL, such aslight/ultralight proppant from various manufacturers, e.g., hollowproppant. In some embodiments, the treatment fluid comprises an apparentspecific gravity greater than 1.3, greater than 1.4, greater than 1.5,greater than 1.6, greater than 1.7, greater than 1.8, greater than 1.9,greater than 2, greater than 2.1, greater than 2.2, greater than 2.3,greater than 2.4, greater than 2.5, greater than 2.6, greater than 2.7,greater than 2.8, greater than 2.9, or greater than 3. In someembodiments where the proppant may be buoyant, i.e., having a specificgravity less than that of the carrier fluid, the term “settling” shallalso be inclusive of upward settling or floating.

In some embodiments herein, a combustible foamed fluid may optionallyfurther comprise fibers and/or fiber mixtures, proppant and/or othermaterials such as particles other than fiber or proppant, dispersed inthe carrier fluid. In embodiments, even in absence of proppant, theconductivity may be optimized by alteration of the fracture walls, forexample by heat, pressure or compounds generated from the combustionreaction of the present energized fluid. In embodiments the intrinsicformation characteristics may provide sufficient conductivity.

The liquid phase of the combustible foamed fluid may include water,fresh water, seawater, connate water or produced water. The liquid phasemay also include hydratable gels (such as guars, polysaccharides,xanthan, hydroxy-ethyl-cellulose (HEC), guar, copolymers ofpolyacrylamide and their derivatives, e.g., acrylamido-methyl-propanesulfonate polymer (AMPS), or other similar gels, or a viscoelasticsurfactant system, e.g., a betaine, or the like), a cross-linkedhydratable gel, a viscosified acid (such as a gel-based viscosifiedacid), an emulsified acid (such as an oil outer phase emulsified acid),and an oil-based fluid including a gelled, foamed, or otherwiseviscosified oil. The liquid phase may be a brine, and/or may include abrine. The liquid phase may include hydrochloric acid, hydrofluoricacid, ammonium bifluoride, formic acid, acetic acid, lactic acid,glycolic acid, maleic acid, tartaric acid, sulfamic acid, malic acid,citric acid, methyl-sulfamic acid, chloro-acetic acid, anamino-poly-carboxylic acid, 3-hydroxypropionic acid, apoly-amino-poly-carboxylic acid, and/or a salt of any acid. Inembodiments, the carrier fluid includes a poly-amino-poly-carboxylicacid, such as a trisodium hydroxyl-ethyl-ethylene-diamine triacetate,mono-ammonium salts of hydroxyl-ethyl-ethylene-diamine triacetate,and/or mono-sodium salts of hydroxyl-ethyl-ethylene-diaminetetra-acetate, or other similar compositions. When a polymer is presentin a low viscosity liquid phase, for example, in some embodiments it maybe present at a concentration below 1.92 g/L (16 ppt), e.g. from 0.12g/L (1 ppt) to 1.8 g/L (15 ppt). When a viscoelastic surfactant is usedin a low viscosity liquid phase, for example, in some embodiments it maybe used at a concentration below 10 ml/L, e.g. 2.5 ml/L to 5 ml/L.

According to some embodiments of the present disclosure, the combustiblefoamed fluid comprises fibers, or may be used with another treatmentfluid or stage or substage comprising fibers. Different types of fibersmay be used optionally at different loadings to provide differentfunctionalities, which may not necessarily be mutually exclusive, to aparticular treatment fluid or stream.

In some embodiments, the treatment fluid comprises from 1.2 to 12 g/L offibers based on the total volume of the carrier fluid (from 10 to 100ppt, pounds per thousand gallons of carrier fluid), e.g., equal to orless than 4.8 g/L of the fibers based on the total volume of the carrierfluid (equal to or less than 40 ppt) or from 1.2 or 2.4 to 4.8 g/L ofthe fibers based on the total volume of the carrier fluid (from 10 or 20to 40 ppt). In some embodiments, the fibers, which may beproppant-suspending carrier and/or non-bridging, are crimped staplefibers. In some embodiments, the crimped fibers comprise from 1 to 10crimps/cm of length, a crimp angle from 45 to 160 degrees, an averageextended length of fiber of from 4 to 15 mm, and/or a mean diameter offrom 8 to 40 microns, or 8 to 12, or 8 to 10, or a combination thereof.In some embodiments, the fibers comprise low crimping equal to or lessthan 5 crimps/cm of fiber length, e.g., 1-5 crimps/cm.

In some embodiments, the fibers may have a length of from about 2 toabout 25 mm, such as from about 3 mm to about 20 mm. In someembodiments, the fibers may have a linear mass density of about 0.111dtex to about 22.2 dtex (about 0.1 to about 20 denier), such as about0.167 to about 6.67 dtex (about 0.15 to about 6 denier).

Depending on the temperature that the treatment fluid will encounterdownhole, including transient temperatures associated with thecombustion of the foamed fluid, the carrier, bridging or non-bridgingfibers may be chosen with an emphasis more on their functionality ascarrier, bridging and/or non-bridging fibers based on their resistanceto degradability at the ambient downhole temperatures and theirdegradability at the temperature and duration of the combustion process.For example, since low, mid or high temperature fibers may be selectedsolely for their treatment functionality and resistance to degradationat the formation temperature, whereas any or all of the low, mid or hightemperature fibers can be degraded at the temperatures associated withthe downhole combustion, e.g., high temperature fibers can be usedregardless of the ambient downhole temperatures, e.g., in low or midtemperature formations, since such fibers might sufficiently degradeupon combustion of the foamed fluid. This provides an example of auniversal fluid that can be used in a wide variety of formations,regardless of the downhole temperature conditions.

Suitable fibers may optionally degrade under ambient downholeconditions, which may include temperatures as high as about 180° C.(about 350° F.) or more and pressures as high as about 137.9 MPa (about20,000 psi) or more, in a duration that is suitable for the selectedoperation, from a minimum duration of about 0.5, about 1, about 2 orabout 3 hours up to a maximum of about 24, about 12, about 10, about 8or about 6 hours, or a range from any minimum duration to any maximumduration.

In some embodiments, the fibers comprise polyester. In some embodiments,the polyester undergoes hydrolysis at a low temperature of less thanabout 93° C. as determined by slowly heating 10 g of the fibers in 1 Ldeionized water until the pH of the water is less than 3, and in someembodiments, the polyester undergoes hydrolysis at a moderatetemperature of between about 93° C. and 149° C. as determined by slowlyheating 10 g of the fibers in 1 L deionized water until the pH of thewater is less than 3, and in some embodiments, the polyester undergoeshydrolysis at a high temperature greater than 149° C., e.g., betweenabout 149.5° C. and 204° C. In some embodiments, the polyester isselected from the group consisting of polylactic acid (PLA),polyglycolic acid (PGA), copolymers of lactic and glycolic acid, andcombinations thereof.

In some embodiments, the fibers may be degradable or non-degradable, andare selected from the group consisting of polylactic acid (PLA),polyglycolic acid (PGA), polyethylene terephthalate (PET), polyester,polyamide, polycaprolactam and polylactone, poly(butylene) succinate,polydioxanone, nylon, glass, ceramics, carbon (including carbon-basedcompounds), elements in metallic form, metal alloys, wool, basalt,acrylic, polyethylene, polypropylene, novoloid resin, polyphenylenesulfide, polyvinyl chloride, polyvinylidene chloride, polyurethane,polyvinyl alcohol, polybenzimidazole,polyhydroquinone-diimidazopyridine,poly(p-phenylene-2,6-benzobisoxazole), rayon, cotton, cellulose andother natural fibers, rubber, and combinations thereof.

In some embodiments, the injection of the treatment fluid including atleast one stage or substage comprising the combustible foamed fluidforms a homogenous region within the fracture of continuously uniformdistribution of the proppant or other solid particulate. In someembodiments, the alternation of the concentration of the agglomerantand/or agglomerant aid forms heterogeneous areas within the fracturecomprising agglomerant/agglomerant aid-rich areas andagglomerant/agglomerant aid-lean areas.

In some embodiments, the agglomerant may comprise a degradable material.In some embodiments, the agglomerant is selected from the groupconsisting of polylactic acid (PLA), polyglycolic acid (PGA),polyethylene terephthalate (PET), polyester, polyamide, polycaprolactamand polylactone, poly(butylene succinate, polydioxanone, glass,ceramics, carbon (including carbon-based compounds), elements inmetallic form, metal alloys, wool, basalt, acrylic, polyethylene,polypropylene, novoloid resin, polyphenylene sulfide, polyvinylchloride, polyvinylidene chloride, polyurethane, polyvinyl alcohol,polybenzimidazole, polyhydroquinone-diimidazopyridine,poly(p-phenylene-2,6-benzobisoxazole), rayon, cotton, or other naturalfibers, rubber, sticky fiber, or a combination thereof. In someembodiments the agglomerant may comprise acrylic fiber. In someembodiments the agglomerant may comprise mica.

In some embodiments, the agglomerant is present in the agglomerant-ladenstages of the treatment fluid in an amount of less than 5 vol %. Allindividual values and subranges from less than 5 vol % are included anddisclosed herein. For example, the amount of agglomerant may be from0.05 vol % less than 5 vol %, or less than 1 vol %, or less than 0.5 vol%. The agglomerant may be present in an amount from 0.5 vol % to 1.5 vol%, or in an amount from 0.01 vol % to 0.5 vol %, or in an amount from0.05 vol % to 0.5 vol %.

In further embodiments, the agglomerant may comprise a fiber with alength from 1 to 50 mm, or more specifically from 1 to 10 mm, and adiameter of from 1 to 50 microns, or, more specifically from 1 to 20microns. All values and subranges from 1 to 50 mm are included anddisclosed herein. For example, the fiber agglomerant length may be froma lower limit of 1, 3, 5, 7, 9, 19, 29 or 49 mm to any higher upperlimit of 2, 4, 6, 8, 10, 20, 30 or 50 mm. The fiber agglomerant lengthmay range from 1 to 50 mm, or from 1 to 10 mm, or from 1 to 7 mm, orfrom 3 to 10 mm, or from 2 to 8 mm. All values from 1 to 50 microns areincluded and disclosed herein. For example, the fiber agglomerantdiameter may be from a lower limit of 1, 4, 8, 12, 16, 20, 30, 40, or 49microns to an upper limit of 2, 6, 10, 14, 17, 22, 32, 42 or 50 microns.The fiber agglomerant diameter may range from 1 to 50 microns, or from10 to 50 microns, or from 1 to 15 microns, or from 2 to 17 microns.

In further embodiments, the agglomerant may be fiber selected from thegroup consisting of polylactic acid (PLA), polyester, polycaprolactam,polyamide, polyglycolic acid, polyterephthalate, cellulose, wool,basalt, glass, rubber, or a combination thereof.

In further embodiments, the agglomerant may comprise a fiber with alength from 0.001 to 1 mm and a diameter of from 50 nanometers (nm) to10 microns. All individual values from 0.001 to 1 mm are disclosed andincluded herein. For example, the agglomerant fiber length may be from alower limit of 0.001, 0.01, 0.1 or 0.9 mm to any higher upper limit of0.009, 0.07, 0.5 or 1 mm. All individual values from 50 nanometers to 10microns are included and disclosed herein. For example, the fiberagglomerant diameter may range from a lower limit of 50, 60, 70, 80, 90,100, or 500 nanometers to an upper limit of 500 nanometers, 1 micron, or10 microns.

In some embodiments, the agglomerant may comprise an expandablematerial, such as, for example, swellable elastomers, temperatureexpandable particles, Examples of oil swellable elastomers includebutadiene based polymers and copolymers such as styrene butadiene rubber(SBR), styrene butadiene block copolymers, styrene isoprene copolymer,acrylate elastomers, neoprene elastomers, nitrile elastomers, vinylacetate copolymers and blends of EV A, and polyurethane elastomers.Examples of water and brine swellable elastomers include maleic acidgrafted styrene butadiene elastomers and acrylic acid graftedelastomers. Examples of temperature expandable particles include metalsand gas filled particles that expand more when the particles are heatedrelative to silica sand. In some embodiments, the expandable metals caninclude a metal oxide of Ca, Mn, Ni, Fe, etc. that reacts with the waterto generate a metal hydroxide which has a lower density than the metaloxide, i.e., the metal hydroxide occupies more volume than the metaloxide thereby increasing the volume occupied by the particle. Furtherexamples of swellable inorganic materials can be found in U.S.Application Publication Number US 20110098202, which is herebyincorporated by reference in its entirety. An example for gas filledmaterial is EXPANCEL™ microspheres that are manufactured by andcommercially available from Akzo Nobel of Chicago, Ill. Thesemicrospheres contain a polymer shell with gas entrapped inside. Whenthese microspheres are heated, e.g., during the combustion stage and/ordue to the ambient formation temperature, the gas inside the shellexpands and increases the size of the particle. The diameter of theparticle can increase 4 times which could result in a volume increase bya factor of 64.

In some embodiments the agglomerants may be gel bodies such as balls orblobs made with a viscosifier, such as for example, a water solublepolymer such as polysaccharide like hydroxyethylcellulose (HEC) and/orguar, copolymers of polyacrylamide and their derivatives, and the like,e.g., at a concentration of 1.2 to 24 g/L (10 to 200 ppt where “ppt” ispounds per 1000 gallons of fluid), or a viscoelastic surfactant (VES).The polymer in some embodiments may be crosslinked with a crosslinkersuch as metal, e.g., calcium or borate. The gel bodies may furtheroptionally comprise fibers and/or particulates dispersed in an internalphase. The gel bodies may be made from the same or different polymerand/or crosslinker as the continuous crosslinked polymer phase, but mayhave a different viscoelastic characteristic or morphology.

In some embodiments, when proppant is present as in the initiation,propagation or other fracture creation operation, the treatment fluid,e.g., the combustible foamed fluid or another treatment fluid or stageor substage associated or used in a treatment job therewith, comprisesfrom 0.01 to 1 kg/L of the proppant based on the total volume of thecarrier fluid in the treatment stream (from 0.1 to 8.3 ppa, poundsproppant added per gallon of carrier fluid), e.g., from 0.048 to 0.6kg/L of the proppant based on the total volume of the carrier fluid inthe dilute stream (0.4 to 5 ppa), or from 0.12 to 0.48 kg/L of theproppant based on the total volume of the carrier fluid in the dilutestream (from 1 to 4 ppa), or from 0.12 to 0.18 kg/L of the proppantbased on the total volume of the carrier fluid in the dilute stream(from 1 to 1.5 ppa). Exemplary proppants include ceramic proppant, sand,bauxite, glass beads, crushed nut shells, polymeric proppant, rod shapedproppant, and mixtures thereof.

In some embodiments the treatment fluid comprising the combustiblefoamed fluid may include a fluid loss control agent, e.g., fine solidsless than 10 microns, or ultrafine solids less than 1 micron, or 30 nmto 1 micron. According to some embodiments, the fine solids are fluidloss control agents such as γ-alumina, colloidal silica, CaCO₃, SiO₂,bentonite etc.; and may comprise particulates with different shapes suchas glass fibers, flocs, flakes, films; and any combination thereof orthe like. Colloidal silica, for example, may function as an ultrafinesolid loss control agent, depending on the size of the micropores in theformation, as well as a gellant and/or thickener in any associatedliquid or foam phase.

EXAMPLES

Any element in the examples may be replaced by any one of numerousequivalent alternatives, only some of which are disclosed in thespecification. Although only a few example embodiments have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exampleembodiments without materially departing from the concepts describedherein. The disclosed subject matter may be embodied in other formswithout departing from the spirit and the essential attributes thereof,and, accordingly, reference should be made to the appended claims,rather than to the foregoing specification, as indicating the scope ofthe disclosed subject matter. Accordingly, all such modifications areintended to be included within the scope of this disclosure as definedin the following claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents, but alsoequivalent structures. Thus, although a nail and a screw may not bestructural equivalents in that a nail employs a cylindrical surface tosecure wooden parts together, whereas a screw employs a helical surface,in the environment of fastening wooden parts, a nail and a screw may beequivalent structures. It is the express intention of the applicant notto invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of theclaims herein, except for those in which the claim expressly uses thewords ‘means for’ together with an associated function.

Example 1 Combustible Fluid Foamed with Stoichiometric Hydrogen/OxygenMix

An electrolysis cell had graphite and copper electrodes with surfacearea of 30 cm² spaced 2 cm apart. The cell was loaded with water andpowered by a DC unit with a voltage or potential of 24 volts. Gas formedin the cell comprising an oxygen/hydrogen mix was transferred to abottle through a plastic tube and bubbled through water containing asodium laurate foaming agent. Bubble size was controlled to 1-2 mm usinga choke at the end of the tube. The foam generation rate was up to 10ml/min of a foam quality of 60% at atmospheric pressure and ambienttemperature.

Example 2 Combustion of Combustible Foam in a Narrow Slot

A 30 ml quantity of the combustible foamed fluid of Example 1 was placedin a 1.5 mm wide slot between opposing 10 cm by 20 cm surfaces ofaluminum foil wrapped construction bricks. The slot was sealed and thefoam was ignited at a side of the slot using a spark igniter. Rapidcombustion of the fluid resulted in complete disappearance of the fluid,which was confirmed by opening and visually inspecting the slot afterthe experiment.

Example 3 Reduction of Foam Volumes

The potential reduction of the volume of the gas phase of foams from thecomplete combustion of stoichiometric fuel/oxygen ratios was estimatedfor some gas fuel sources. The estimations assumed the same before andafter pressures and temperatures, that the volume of liquid waterproduced as a combustion product was negligible compared to the initialgas phase volume in the foam, that the carbon dioxide produced as acombustion product was in gas form and/or at least partially soluble inany liquid present, and that all gases in the fluid before and aftercombustion followed the ideal gas law (PV=nRT). The estimated resultsare presented in the following Table:

TABLE Combustion Reaction Gas phase volume reduction (%) 2H₂ + O₂ →2H₂O >99 CH₄ + 2O₂ → CO₂ + 2H₂O >67 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O >56 C₂H₄ +3O₂ → 2CO₂ + 2H₂O >50 2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O >43

Although the preceding description has been described herein withreference to particular means, materials and embodiments, it is notintended to be limited to the particulars disclosed herein; rather, itextends to all functionally equivalent structures, methods and uses,such are within the scope of the appended claims.

1. A treatment method, comprising: introducing downhole a quantity of atreatment fluid comprising a combustible foamed fluid comprising amixture of a fuel source and a combustion oxidant source, wherein a gasphase of the foam comprises the mixture of the fuel source and thecombustion oxidation source; placing the combustible foamed fluid in adownhole structure under non-combustion conditions free of an activeignition source; thereafter igniting the combustible foamed fluid tocombust the fuel source in the downhole structure forming apost-combustion fluid.
 2. (canceled)
 3. The method of claim 1, whereinthe combustion decomposes the foamed fluid.
 4. The method of claim 1,further comprising cooling the post-combustion fluid to a reducedspecific volume relative to the combustible foamed fluid.
 5. The methodof claim 1, wherein the treatment fluid further comprises proppant. 6.The method of claim 1, wherein the downhole structure comprises afracture above a fracturing pressure.
 7. The method of claim 1, whereinthe downhole structure comprises a formation matrix below a fracturingpressure.
 8. The method of claim 1, wherein the fuel source is selectedfrom hydrogen, hydrocarbon gases, or a mixture thereof.
 9. The method ofclaim 1, wherein the combustion oxidant source comprises molecularoxygen.
 10. The method of claim 1, further comprising preparing thecombustible foamed fluid at a surface location and introducing themixture into a wellbore.
 11. The method of claim 1, further comprisingintroducing the combustion oxidant source into a wellbore in a firststream separate from a second stream comprising the fuel source, andmixing the first and second streams downhole to form the combustiblefoamed fluid.
 12. An energized fluid system, comprising: a combustibleenergized fluid comprising a combustible gaseous mixture dispersed in acontinuous liquid phase; a downhole structure to receive the combustiblefoamed fluid under non-combustion conditions free of an active ignitionsource; and an ignition source in communication with the downholestructure activatable to initiate combustion of the dispersed gaseousmixture.
 13. The energized fluid system of claim 12, wherein thecombustible gaseous mixture comprises oxygen mixed with a fuel sourceselected from hydrogen, hydrocarbon gases and combinations thereof. 14.The energized fluid system of claim 12, wherein the downhole structurecomprises a formation matrix.
 15. The energized fluid system of claim12, wherein the structure comprises a fracture.
 16. The energized fluidsystem of claim 12, further comprising a controller to remotely activatethe ignition source, wherein the ignition source comprises an electricalor chemical igniter.
 17. A method, comprising: dispersing a gaseous fuelsource and a gaseous combustion oxidant source into a continuous liquidphase to form a combustible foamed fluid; and isolating the combustiblefoamed fluid in a downhole structure under non-combustion conditionsfree of an active ignition source.
 18. The method of claim 17, whereinthe gaseous fuel source and gaseous combustion oxidant are delivered inseparate streams through a wellbore and mixed downhole.
 19. The methodof claim 17, wherein the gaseous fuel source comprises hydrogen, thegaseous combustion oxidant comprises oxygen, and the continuous liquidphase comprises water, and further comprising passing the liquid phasethrough an electrolysis cell to generate the oxygen and hydrogen in theliquid phase.
 20. The method of claim 17, wherein the downhole structurecomprises a fracture above a fracturing pressure, or a formation matrixbelow the fracturing pressure.